diff options
| author | Shaohua Li <shli@fb.com> | 2017-12-20 11:10:17 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-12-20 11:10:17 -0700 |
| commit | 111be883981748acc9a56e855c8336404a8e787c (patch) | |
| tree | fe3766fcad8f4996f049d2562ad0d62b7bb8fc98 /block | |
| parent | 0abc2a10389f0c9070f76ca906c7382788036b93 (diff) | |
block-throttle: avoid double charge
If a bio is throttled and split after throttling, the bio could be
resubmited and enters the throttling again. This will cause part of the
bio to be charged multiple times. If the cgroup has an IO limit, the
double charge will significantly harm the performance. The bio split
becomes quite common after arbitrary bio size change.
To fix this, we always set the BIO_THROTTLED flag if a bio is throttled.
If the bio is cloned/split, we copy the flag to new bio too to avoid a
double charge. However, cloned bio could be directed to a new disk,
keeping the flag be a problem. The observation is we always set new disk
for the bio in this case, so we can clear the flag in bio_set_dev().
This issue exists for a long time, arbitrary bio size change just makes
it worse, so this should go into stable at least since v4.2.
V1-> V2: Not add extra field in bio based on discussion with Tejun
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: stable@vger.kernel.org
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/bio.c | 2 | ||||
| -rw-r--r-- | block/blk-throttle.c | 8 |
2 files changed, 3 insertions, 7 deletions
diff --git a/block/bio.c b/block/bio.c index 8bfdea58159b..9ef6cf3addb3 100644 --- a/block/bio.c +++ b/block/bio.c @@ -599,6 +599,8 @@ void __bio_clone_fast(struct bio *bio, struct bio *bio_src) bio->bi_disk = bio_src->bi_disk; bio->bi_partno = bio_src->bi_partno; bio_set_flag(bio, BIO_CLONED); + if (bio_flagged(bio_src, BIO_THROTTLED)) + bio_set_flag(bio, BIO_THROTTLED); bio->bi_opf = bio_src->bi_opf; bio->bi_write_hint = bio_src->bi_write_hint; bio->bi_iter = bio_src->bi_iter; diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 825bc29767e6..d19f416d6101 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -2226,13 +2226,7 @@ again: out_unlock: spin_unlock_irq(q->queue_lock); out: - /* - * As multiple blk-throtls may stack in the same issue path, we - * don't want bios to leave with the flag set. Clear the flag if - * being issued. - */ - if (!throttled) - bio_clear_flag(bio, BIO_THROTTLED); + bio_set_flag(bio, BIO_THROTTLED); #ifdef CONFIG_BLK_DEV_THROTTLING_LOW if (throttled || !td->track_bio_latency) |